The present invention relates to a fluid control valve comprising a control slider that is arranged in a cylinder bore between a pressure fluid inlet and a pressure fluid outlet and that is displaceable in opposition to the force of a preloading device from an opened position, in which inlet and outlet are interconnected, into a closing position in which it isolates the inlet from the outlet, by virtue of exerting the output pressure on an end surface of the control slider confining a fluid chamber. The housing accommodates the serial connection of the fluid chamber, a first portion of the cylinder bore, an annular extension of the cylinder bore terminating into which is the inlet, a second portion of the cylinder bore terminating into which is the outlet, and a bore receiving the preloading device into which a leakage oil port terminates. The control slider includes at least one recess which is isolated from the end surfaces by way of first and second areas conformed to the cylinder bore, and which recess is allocated to the outlet in the closing position.
Fluid control valves are actuated in response to at least one varying fluid pressure in order to control the fluid pressure and/or the fluid flow in a connected system. Normally such pressure functions to displace a control piston, designed for example as control slider, which changes the opening cross-sections of fluid ports. In a pressure-reducing valve, for example, there is provided a spring assembly which acts on the control slider in opposition to the force caused by the output pressure. The control slider in a pressure-reducing valve is movable by the output pressure into the closing position in opposition to the force of the spring assembly.
In German printed and published patent application No. 32 22 860, a fluid control valve is disclosed in which the control slider includes areas of like diameter conformed to the diameter of the cylinder bore. One of the areas isolates the inlet from the outlet in the closing position, while another one thereof isolates the outlet from a portion of the cylinder bore communicating with a leakage oil port. The portions of the cylinder bore which cooperate with the areas of the control slider are of like diameter. The quantity of leakage oil passing through between inlet and outlet may result in an increase of the output pressure. Therefore, a quantity of leakage oil is allowed to flow off to the leakage oil port. However, maintaining a predetermined output pressure tolerance necessitates a nigh quantity of leakage oil flowing off to the leakage oil port. This is a problem.
It is an object of the present invention to provide a fluid control valve of the type referred to which ensures that the output pressure is maintained exactly while only small leakage oil losses occur.